the
scientific
landscape
 modeling 
representation
(models, semantics)
 semiotics 
logic &
reasoning
complexity & metrics math. objects
categories
relations
objects
wholes & levels
meaning
meta
linguistic
glossary
formalization
& symbol
manipulation
components & datatypes relations
 ontology 
truth & reality
algebras
Location: http://www.cs.mun.ca/~ulf/gloss/repres.html. By Ulf Schünemann since 2002. Please mail any comments.

Representation: Models and/or Semantics

  1. Specialized Languages - Why?
  2. Knowledge Symbolization Levels
  3. Signs, Information, Representation
  4. Representation in a System I: Signals as Indexical Signs - Meaning by Effective Coupling
  5. Representation in a System II: Signs Meaning by Non-Effective Coupling
  6. Representation in a System III: Knowledge Representation Knowing

Object-oriented programming and physical models -> moved to system modeling: the paradigms.
[ATO] -> moved to bib collection file.


Specialized Languages - Why?

[ACG] W M McKeeman, J J Horning, D B Worman: A Compiler Generator; Prentice-Hall 1970. «The users of a modern computer faces a bewileering array of languages: languages of machine control; high-level languages, which must be translated; languages to express the translation process; and languages to define languages. All these languages are artificial, restricted modes of expression first invented by someone and the tediously learned by others. One feels obliged to asky why so many artificial languages have been created ... The answer is that everyone invents languages all the time. Computer users, because they face particularly severe obstacles in the process [of language invention], are more likely to notice that they are doing so. However, they should not avoid language invention. And, indeed, they cannot.
Mind creates languages; it is part of the process of understanding. Only representations of objects and ideas can exist in the brain, and while we do not know how these representations are "manipulated," we do know that it is helpful to have symbols, which we can record, observe, and manipulate. These we invent.
We may coin a word (cybernetics or beatnik) or a complete jargon (listen to a stockbroker, for example); we may devise a new symbol () or a whole formal mathematical system (tensor calculus); or we may assign new meanings to old forms (what does "cool" mean?). There are examples of invented languages in law and differential calculus, knitting and matrix algebra, mathematical logic and organic chemistry. In each case the invented language has special symbolic properties that simplify communication and comprehension.» [ACG:2]

For example:

  • «Organic Chemistry: 3CH3CH2OH + Cr2O7- - + 8H+ --> 3CH3CHO(g) + 2Cr+3 + 7H2O
  • Knitting: K2 tog. 3(5) times, *k1, p2, k1, k3, tog., k1, p2, k1, p1, k1, p3 tog., k1, p1, k1, p1*; repeat between *'s once more, k1, p2, k1, k3 tog., k1, p2, k1; k2 tog. 3(5) times; 47(51) sts. (Note that there are two levels of understanding; we may either give explicit directions or say just "Knit a ski cap.")
  • Poetry: Shakespearean sonnets are in iambic pentameter and consists of three quatrains followed by a couplet» [ACG:3f].

    «That the computer ... has manlike properties should not surprise us. It was invented to do intellectual work for us. Thus, we are naturally antropomorhic in our description and understanding of computers. In particular, we expect to carry on an extensive symbolic dialogue with our computers in languages acceptable to us (problem languages). ...
    Each computer has its own control language, usually quite remote from the wide variety of languages demanded by the diverse uses of the machine. A translation from problem language to machine language is required. Assemblers, interpeters, and compilers have been developed to transfer as much as possible of this tedious task from man to machines» [ACG:4f]


    Knowledge Symbolization Levels

    There are five language levels w.r.t. to symbolizing/representing/expressing knowledge [FO 632f]
    level primitives interpretation main feature
    logical predicates, functionsarbitrary formalization
    epistemological structuring relationsarbitrary structure
    ontological ontological relationsconstrainedmeaning
    conceptual conceptual relationssubjective = psychological?conceptualization
    linguistic linguistic terms subjective = cultural?language dependency
    1. «At the (first order) logical level, the basic [language] primitives are predicates and functions, which have given a formal semantics in terms of relations among objects of a domain. No particular assumption is made however on the nature of such relations, which are completely general and content-independent. The logical level is the level of formalization: it allowsfor a formal interpretation of the primitives, but their interpretation remains totally arbitrary.»
      For example, at the logical level `a red ball' could be represented as x. Ball(x) & Red(x).
    2. At the epistemological level «the [language] primitives allow to specify "the formal structure of conceptual units and their interrelationships as conceptual units (independeent of any knowledge expressed therein)". In other wordls, while the logical level deals with abstract predicates and the conceptual level with specific concept, at the epistemolofical level the generic notion of a concept is introduced as a knowledge structuring primitive. Concepts themselves--which correspond to unary predicates at the logical level--have an internal structure, as they "bundle" together further concepts or binary relations (roles). The epsitemological level is tehrefore the level of structure
      For example, it could be declared that in x. Ball(x) & Red(x) (logical level), Ball is a concept and Red is a filler of a Colour role.
    3. «At the ontolological level, such ontological commitments associatied to the language primitives are specified explicitly. Such a specification can be made in two ways: either by suitably restricting the semantics of the primitives, or by introducing meaning postulates expressed in the language itself. In both cases, the goal is to restrict the number of possible interpretatoins, characteriying the meaning of the basic ontological categories used to describe the domain: the ontological level is therefore the level of meaning. Of course such a characterization will be in general incomplete, and the result will be an approximation of the set of intended models. ...»
      For example, it could be fixed what concepts, roles and role-fillers are, rendering it impossible to declare (at the epistemological level) Red not as a role-filler but as a concept in accordance with the sense of "red" we have in mind.
    4. «At the conceptual level, primitives have a definite cognitive interpretation, corresponding to language-independent concepts like elementary actions or themaic roles. The skeleton of the domain structure is already given, independently of an explicit account of the underlying ontological assumptions. Within a certain application domain, the user is forced to express knowledge in the form of a specialization of this skeleton. ...»
      For example, a set of concepts and roles can be pre-defined like PhysicalBody and Colour, if they are agreed to be standard to a domain. «However, our chances of getting such an agreement ... [depends] in thic case on the principles we have adopted for the definition of our basic ontological categories ... Notice that the necessity of well-founded principles is much more relevant if we want to further specialize logical relations into categories like parts, qualities, properties, states and so on.»
    5. «Finally, primitives at the linguistic level directly refer to verbs and nouns.»
    Ontological distinctions «allow the knowledge engineer to make clear the intended meaning of a particular symbol. This is especially important since we are constantly using natural language words for predicate symbols, relying on them to make our statements readable and to convey meanings not explicitly stated. However, since words are ambiguous in natural language, it may be important to "tag" these words with a semantic category, in assoication with a suitable axiomatisation, in order to guarantee a consistent interpretation» [FO 636].

    Signs, Information, Representation

    moved to T.W.O.

    Representation in System I: Signals as Indexical Signs - Meaning by Effective Coupling

    [This section is here until it finds a better place]

    -> eg. in JSD: give meaning to system environment description (abstract model) by connecting computer system with its environment (concrete model)

    In (ultimate) system theory, meaning of signals/signs in an information system is treated as follows:

    Take 1. A system (core) S may react to a situation a by action z through a control chain a -> ... -> x -> ... -> z. The intermediate, system-internal signal x can be considered a sign with two meanings to S (sign interpretant):
    - the situation a ("cognitive meaning"), and
    - the action z ("intentional meaning") [SuB 328].
    (This is in the ideal case - in reality, preceived sitation a may deviate from actual situation a', and intended behavior z may deviate from actual behavior z'.)
    The semantic quality which a sign x, like pointer angle, has is the organetic quality of the designate a (e.g., car speed), or z, respectively.

    Take 2. Any signal x is semanticable (potential sign?) if it is in the system "core" S (sign interpretant) and is "relevant" to S, ie., affects its fitness. Now let x be a semanticable sign signal which is conductor of a "homoeostatic dyad" <a;z> (see below) in an idealized model. The meaning of x is a semantically encoded description of a or z wrt. a's interference with z's homoeostatis.
    - x's cognitive meaning is the description of a ("valence" of a wrt. z)
    - x's intentional meaning is the description of z ("problem" of z wrt. a) [SuB 359].
    Hence meaning is a function of the system's structure [SuB 361].

    A homoeostatic dyad <a;z> is a noisefree homoeostatic subsystem with source a and sink z [SuB 338]. There are three type K(1) control blocks (subsystems) which can establish homoestatic dyads [SuB 335] (shown in form of Mason diagrams):
    homoeostatic mesh homoeostatic cycle
    (negative feedback loop)
    homoeostatic net
    .---------------v
    a ----> z       x
            ^-------'
    
    a ----> z ----> x
            ^-------'
    
    .---------------v
    a ----> z ----> x
            ^-------'
    
  • a is the free input signal, the source of the homoeostatic entropy.
  • z is the "homoeostatic variable", which depends on a and x in a way that their possible changes are neutralized (the sink of the homeostatic entropy).
  • x is the "conductor" of the homoeostatic entropy, i.e., depends on a and affects z.

  • Representation in System II: Sign Meaning by Non-Effective Coupling

    A technical example [OOO 206]: a file cache is always consistent if all reads and write to the cache go through to the disk, ie. an effective coupling (but then there were no caching). A cache optimizes this by not reading and writing the content of the file but some complex but fast coordination mechanism. The purpose of caching is that the file can be obtained from the cache without needing to access the disk (except at those time it knows the file's contents on the disk has changed, then it does resynchronize with the disk). IOW a cache continues to track the contents of a file on the disk without being all the time effectively coupled to the disk.
    Sunflowers rotate their head to follow the sun, and, let's assume, stand still when the sun is hidden (behind a tree, house, etc.). The super-sunflower continues rotating even while the sun is hidden. «What distinguishes super-sunflowers is not the fact that they track the sun. ... [T]hey track something to which they are not effectively coupled. This behavior, which I will call "non-effective coupling," is no less than the forerunner of semantics: a very simple form of effect-transcending coordination in some way essential to the overall existence or well-being of the constituted system» [
    OOO 203].
    «There is nothing more basic to intentionality than this pattern of coming together and coming apart, at one moment being fully engaged, at another point being separated, but separated ... in a way as to stay corrdinated with what at the moment is distal and beyond effective reach» [OOO 206]. «[T]his coordination will in general be approximate. ... [C]oordination can only settle on some but not all aspects of the distal sitatuation» [OOO 207].
    «[T]he super-sunflower, when it can no longer be driven by the incident radiation, has to employ a different, internal mechanism ... in order to continue to "track" the sun. This retractionof responsibility into the s-region, as I will call it---this shouldering of effective responsibility by the s-region, to compensate for the break in effective coupling---is not less than the origin of reasoning, representation and syntax: effective projection, onto the intentional agent, of the requisite arrangements for maintaining long-distance (semantic) coherence» [OOO 221].
    «[R]esponsibility for mainining coordination across the gap is asymmetrical. It "falls to the s-region," one might say---except that gets it backwards. Rather: to be an s-region is to assume this responsibility. ... [T]he "distance" over which the s-region is able to maintain coordination will depend on its cleverness---not just its internal cleverness, but the total sophistication of the environment and cultural resources on which it can lay its hands» [OOO 223f].

    Representation in System III: Knowledge Representation Knowing

    About neural network models: «One area that is disturbing is that neither the network nor the programmer have easy access to the information structures stored in the weights of the hidden layer. For example, if the network learns to distinguish the sonar echoes of different types of rocks and mines, the information for all the different kinds of rocks and mines in the training set will be superposed across the entire network. There is no easy way to extract from the network the features of the mines that enable them to be distinguished. ... [E]ven though the network can clearly distinguish the mines from the rocks, there is an important sense in which the network doesn't 'know' anything about the usual or unusual shapes for rocks or mines.
    Cussins (1990) offers an interesting distinction between the conceputal and nonconceptual content of a system that may help to clarify the problem. ... [O]ur rock and mine connectionist system has the property of being able to distinguish rocks and mines, but the system itself need not have the concepts of rocks and mines in order to have the property to distinguish them. Such a system 'knows its way around' a domain, but lacks the concepts to describe what it knows. First-order connectionist networks are ideal contenders for systems capable of supporting nonconceptual content.
    The problem with nonceptual content is that there is no access to the information that enables the system to negotiate a domain. ... [On the other hand it] seems that part of the ability to adapt to change is to isolate and manipulate information and knowledge. Andy Clark (1993) discusses Cussins' criteria ...:
    "Cussins offers a rather intricate account in which one of the leading ideas is that to have a conceptual content requires more than a mere causal or informational link to the state of the world implicated in the description of the content. To have (properly) the concept 'fly' involves more than being able to find your way around (like a frog) in a fly-infested domain. It involves having a whole web of concepts in which your concept of a fly is embedded. In particular, it involves having your fly concept at the disposal of any other conceptual abilities you have."
    This description of conceptual content sound very like the "knowledge-level" approach in traditional AI.» [
    CGPPF]

    Connectionist networks and knowledge representation: «There is a growing trend in the connectionist literature to reject the kind of ontological engineering required in representing large amounts of knowledge for traditional AI projects. ... However, despite the power of connectionist systems to model learning and categorization, I blieve that it is a mistake to reject outright the "knowledge-level" approach. ...
    ... Some analysis is required in determining the architecture of the network, the selection and encoding of the input data, and the category that each data entry represents. But the actual set of weights in the network that 'represents' the different concepts are not pre-determined. Clearly in a connectionist system the level of representation is finer-grained than one at the knowledge-level. For this reason, connectionist networks are often said to work at the sub-symbolic or sub-linguistic level and to use micro-features in categorization.
    Connectionist systems are massively parallel networks where information is stored in parameters associated with connections rather than in the elements themselves. Thus, connectionist networks do not involve computations defined over symbols. ... Basically, neural networks are good at many of the tasks traditional AI programs are so bad at: pattern recognition, learning and generalization» [CGPPF].


    Ulf Schünemann 201202